docs: def _set_parameter(encoder, parameter, parameter_name, val):
      """
      This helper function sets a specific Brotli encoder parameter, checking
      the return code and raising :class:`Error <brotli.Error>` if it is
      invalid.
      """
      rc = lib.BrotliEncoderSetParameter(encoder, parameter, val)
  
      if parameter == lib.BROTLI_PARAM_MODE:
          _validate_mode(val)
      elif parameter == lib.BROTLI_PARAM_QUALITY:
          _validate_quality(val)
      elif parameter == lib.BROTLI_PARAM_LGWIN:
          _validate_lgwin(val)
      elif parameter == lib.BROTLI_PARAM_LGBLOCK:
          _validate_lgblock(val)
      else:  # pragma: no cover
          raise RuntimeError("Unexpected parameter!")
  
      # This block is defensive: I see no way to hit it, but as long as the
      # function returns a value we can live in hope that the brotli folks will
      # enforce their own constraints.
      if rc != lib.BROTLI_TRUE:  # pragma: no cover
          raise Error(
              "Error setting parameter %s: %d" % (parameter_name, val)
          )